Large EL panel and manufacturing method therefor

ABSTRACT

The invention provides a circuit section of a TFT layer disposed behind an adjacent EL display device, so that a gap defined between pixels at peripheries of the adjacent EL display devices may be 10 μm. Thus, four EL display devices appear to be unified, forming a large EL display panel. In addition, in the case in which a plurality of EL display devices are arranged in a matrix pattern, pitch between the pixels provided in the pixel section of the TFT array is maintained constant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a large EL panel formed by a pluralityof EL display devices, such as organic EL panels, which are arranged ina matrix pattern, and also relates to a manufacturing method for thelarge EL panel.

2. Description of the Related Art

Small EL flat panels (EL display devices) driven by polysilicon TFTs areusually laminated on a hard and transparent substrate by an adhesive,etc., in order to maintain the flatness thereof. Each of the TFTscontrol the driving of one of multiple pixels in the EL display devices,so that plane images are displayed.

The EL display devices are described above are typically two to sixinches in length measured in a diagonal direction, and providedexcellent functions as small image displays.

Conventionally, in theaters and stadiums, large screens, which arecapable of displaying clear images, are commonly used in place ofelectrical scoreboards. In such large screens, a plurality of lightsources, such as the above-described EL display devices, light bulbs arearranged in a matrix pattern. Each of the light sources functions as apixel for forming an image.

In such theaters and stadiums, there is a sufficient distance betweenthe screen and the audience; therefore, the EL display devices having adiagonal length of, for example, several inches should not be a problem.

Recently, on the other hand, instead of CRTs, liquid crystal displaypanels have been commonly used as displays for televisions and personalcomputers. In addition, there has been a demand to increase the sizes ofthe liquid crystal display panels.

In a liquid crystal display, an additional light source is required as abacklight. Thus, to increase the size of the liquid crystal display, thesize of the backlight must also be increased. The present situation,however, is such that when a large (50 to 100 inches in diagonal length)and thin display is required, an amount of heat, which increases alongwith the size of the backlight, will be too large. In addition, thethickness of the display cannot be made thin enough to satisfy therequirement.

Accordingly, the use of the EL display devices driven by TFTs, whichwill be referred to as TFT-EL display devices in the followingdisclosure, has been considered. In the TFT-EL display devices, thebacklights are not required. In addition, due to the use of the TFTs,the number of pixels may be increased, and response rate become higher,so that high-resolution images may be displayed.

Large TFT-EL display devices, however, have not been realized.Accordingly, to form a large display panel which is 20 to 100 inches indiagonal length, small TFT-EL display devices, which are several inchesin diagonal length, must be arranged in a matrix pattern.

Generally, a TFT-EL display device is laminated on a flat-typetransparent substrate. Accordingly, TFT-EL display devices cannot bearranged in proximity to each other beyond the peripheries of thetransparent substrates.

In addition, a TFT array includes not only a pixel section but also acircuit (driver) section for individually controlling the light emissionat the pixels. The circuit section is disposed at a region outside of animage forming area, and prevents the adjacent EL display devices frombeing arranged in close proximity to each other.

In consideration of the above-described structures and theirlimitations, an object of the present invention is to provide a large ELdisplay panel and a manufacturing method thereof, in which a pluralityof EL display devices are arranged in a matrix pattern, and in which apitch between the pixels in the pixel section of the TFT array ismaintained constant.

DISCLOSURE OF INVENTION

The present invention provides a large EL panel including a plurality ofEL display devices which are arranged in a matrix pattern on a maintransparent substrate which is capable of supporting multiple EL displaydevices. Each of the EL display devices includes: a base layer overwhich a luminescent material is applied; an electrode layer which islaminated on one side of the base layer; and a TFT layer. The TFT layerincludes a circuit section in which light emission of the luminescentmaterial is controlled by applying a predetermined voltage between theelectrode layer and the TFT layer and a pixel section which issuperimposed over the other side of the base layer and which is providedwith a plurality of pixels which divide the base layer into sections sothat light emission of the luminescent material in each section isindividually controlled by generating a potential difference between theelectrode layer and the TFT layer at the corresponding section. Thecircuit section of the TFT layer, which is disposed at the regionoutside a light emitting area, is disposed behind the adjacent ELdisplay device so that light emitting areas of the adjacent EL displaydevices are arranged in proximity to each other and separated by apredetermined gap.

In addition, the present invention also provides a manufacturing methodfor a large EL panel in which a plurality of EL display panels are used,each of the EL display panels being constructed of the above-describedEL display device and a sub-transparent substrate that supports the ELdisplay device. The manufacturing method for the large EL display panelincludes the steps of: removing the EL display devices from thesub-transparent substrates; arranging the obtained EL display devices ona main transparent substrate, which is broader than the sub-transparentsubstrate, in a matrix pattern and in a manner such that light emittingareas of the adjacent EL display devices are in proximity to each other;and disposing and fixing the circuit section of the TFT layer, which isdisposed at the region outside the light emitting area, behind theadjacent EL display device.

In the case in which a large display panel is formed by using the ELdisplay devices, a problem has occurred that sub-transparent substrates,which are larger than the EL display devices, prevent the EL displaydevices from being arranged in proximity to each other. Accordingly, byapplying, for example, separation and transfer techniques described inJapanese Unexamined Patent Application Publication Nos. 10-125930 and10-125931, it is possible to arrange the EL display devices in proximityto each other.

With the above-described techniques, the EL display devices may beseparated from the sub-transparent substrates by applying a mechanicalor chemical force to adhesive layers which are disposed therebetween,and may be transferred to another substrate.

Each of the TFT layers has a pixel section and a circuit section. Thepixel section is superimposed over the light emitting area, so that noproblems occur. In contrast, however, the circuit section is disposed atthe periphery, usually at two sides, of the TFT layer, and at the regionoutside the light emitting area. Accordingly, the circuit sectionprevents the adjacent EL display devices from being arranged inproximity to each other, so that the ability of the TFTs to displayhigh-resolution images cannot be sufficiently exploited. According tothe present invention, however, the circuit section is disposed behindthe adjacent EL display device, so that a high resolution and large ELdisplay panel may be constructed.

The manufacturing process of the large EL display panel will bedescribed below. First, the EL display devices are removed from thesub-transparent substrates by using the above-described separation andtransfer technique. Then, the EL display devices are arranged on a maintransparent substrate, which is broader than the sub-transparentsubstrate, in a matrix pattern in a manner such that the light emittingareas of the adjacent EL display devices are in proximity to each other.Then, the circuit section of the TFT layer, which is disposed at theregion outside the light emitting area, is disposed and fixed behind theadjacent EL display devices.

According to the present invention, the EL display devices are severalinches in diagonal length, and the main transparent substrate is 20 to100 inches in diagonal length.

In addition, the predetermined amount of gap between the light emittingareas of the EL display devices is approximately the same as the pitchbetween pixels provided in the pixel section of the TFT layer.

To dispose the circuit section behind the adjacent EL display device,the TFT layer is bent at the boundary between the pixel section and thecircuit section.

Alternatively, a step portion that changes the positions of the adjacentEL display devices in the thickness direction may be provided so as todispose the circuit section behind the adjacent EL display device.

Alternatively, the adjacent EL display devices may be inverted so as toarrange the base layers of the adjacent EL display devices in the sameplane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a large EL panel according to a firstembodiment of the invention;

FIG. 2 is an enlarged view of a portion of FIG. 1;

FIG. 3 is a sectional view of an EL display device;

FIG. 4 is a sectional view of the EL display device and asub-transparent substrate, which are separated from each other;

FIG. 5 is a sectional view of EL display devices which are adjacentlydisposed on a main transparent substrate;

FIG. 6 is a perspective view showing a manner in which circuit sectionsof TFT layers are disposed under the adjacent EL display devices;

FIG. 7 is a front view of the EL display devices which are disposedadjacently to each other on the main substrate;

FIG. 8 is a detailed sectional view of the adjacent EL display deviceswhich are disposed on the main substrate;

FIG. 9 is a sectional view of a large EL panel according to a secondembodiment of the present invention, showing a structure in which thecircuit section of the TFT layer is disposed;

FIG. 10 is a sectional view of a large EL panel according to a thirdembodiment of the present invention, showing a structure in which thecircuit section of the TFT layer is disposed;

FIG. 11 is a front view of TFT layers including circuit sections, whichare incorporated in a fourth embodiment of the present invention;

FIG. 12 is a front view of TFT layers including circuit sections, whichare incorporated in a fifth embodiment of the present invention;

FIG. 13 is a chart showing a manufacturing process for EL panels.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained below in conjunction with theaccompanying drawings.

(First Embodiment)

FIG. 1 shows a large EL display panel 10 according to the presentembodiment. The large EL display panel 10 includes a main transparentsubstrate 12 on which four EL display devices 14A, 14B, 14C, and 14D arearranged in a matrix pattern (in the present embodiment, x×y=2×2). TheEL display devices 14A, 14B, 14C, and 14D have the same structure, andare denoted as EL display devices 14 below when they are genericallydescribed.

As shown in FIG. 2, the EL display device 14, which are driven bypolysilicon TFTs, are divided into a plurality of pixels, and lightemission (and gradation) at each pixel is controlled individually. TheEL display devices 14 are limited in size: a single EL display device isseveral (2 to 6) inches in diagonal length. Thus, to form a display,which is, for example, a dozen inches to a hundred inches in diagonallength, a plurality of EL display devices 14 must be arranged in amatrix pattern.

In FIG. 1, a display which is approximately 20 inches in diagonal lengthis constructed by the four EL display devices 14. This size isapproximately the same as the size “A3” according to the JapaneseIndustrial Standard (JIS).

FIG. 3 shows a sectional view of one of the EL display devices 14.

The EL display device 14 incorporated in the present embodiment isprepared as a product, that is, an EL panel 16, in which the EL displaydevice 14 is laminated on a sub-transparent substrate 18 via an adhesivelayer 20.

More specifically, in the EL panel 16, the EL display device 14 issupported by the sub-transparent substrate 18 in a manner such that theEL display device 14 is parallel to the sub-transparent substrate 18. Inthe present embodiment, the EL display device 14 is separated from thesub-transparent substrate 18 at the adhesive layer 20, as shown in FIG.4. By using a separation and transfer technique, only the EL displaydevice 14 is removed from the sub-transparent substrate 18.

The EL display device 14 is constructed of a laminate including aplurality of layers.

The bottom layer of the EL display device 14 is a TFT layer 22 whichincludes a pixel section 22P and a circuit section 22C. The pixelsection 22P is divided in a matrix pattern, and is provided with aplurality of pixels. Light emission of a fluorescent material, whichwill be described below, at each pixel is controlled individually.

The circuit section 22C includes a driver that controls the lightemission at each pixel, and is disposed along two adjoining sides of theTFT layer 22.

A base layer 24 on which the fluorescent material is applied islaminated over the pixel section 22P of the TFT layer 22. In addition, atransparent electrode layer 26 is laminated so as to cover both the baselayer 24 and the circuit section 22C. The transparent electrode layer 26also functions as a protective layer.

When a current is applied to some particular pixels by the driverincluded in the circuit section 22C of the TFT layer 22, a potentialdifference is generated between the TFT layer 22 and the transparentelectrode layer 26. Accordingly, the fluorescent material contained inthe base layer 24 at the corresponding positions emits light. In thepresent embodiment, the pixels are divided into groups of three, eachgroup providing three colors, RGB, so that color images may bedisplayed.

Now, the above-described case is considered in which the four EL displaydevices 14 are arranged and laminated on the main transparent substrate12 via an adhesive layer 28. In such a case, the circuit section 22C ofthe TFT layer 22 would cause a large gap between the pixels disposed atthe peripherals of two adjacent EL display devices 14. Thus, in thepresent embodiment, the TFT layer 22 is bent at the boundary between thecircuit section 22C and the pixel section 22P so as to dispose thecircuit section 22C behind the adjacent EL display device 14, as shownin FIGS. 5 to 7. Accordingly, the pixels at the peripheries of adjacentEL display devices 14 may be arranged in proximity to each other.

As shown in FIG. 8, the gap between the pixels at the peripheries ofadjacent EL display devices 14 may be reduced to 10 μm. The pitchbetween the pixels is 50 μm, the thickness of the TFT layers is 1 μm,and the thickness of the EL display devices 14 is 5 μm.

The operation of the present embodiment will be explained below inconjunction with a manufacturing process of the large EL display panel10.

First, a plurality of EL panels 16 is prepared so that a display havinga desired diagonal length will be obtained. In the present embodiment,four EL panels 16 are prepared.

In each of the EL panels 16, the required EL display device 14 islaminated on the sub-transparent substrate 18 by the adhesive layer 20.The EL display device 14 is removed from the sub-transparent substrate18 at the adhesive layer 20 by applying the above-described separationand transfer technique.

The EL display devices 14 obtained from the EL panels 16 are arranged onthe main transparent substrate 12 in a matrix pattern (2×2).

At this time, the circuit section 22C of the TFT layer 22 would overlapon the adjacent EL display device 14. To avoid this, the TFT layer 22 isbent at the boundary between the circuit section 22C and the pixelsection 22P so as to dispose the circuit section 22C behind the adjacentEL display device 14.

The four EL display devices 14 are laminated on the main transparentsubstrate 12 by the adhesive layer 28 in a similar manner.

Accordingly, the circuit sections 22C of the TFT layers 22 are disposedbehind the adjacent EL display devices 14, so that the gap between thepixels at the peripheries of the adjacent EL display devices 14 may be10 μm. Thus, the four EL display devices 14A, 14B, 14C, and 14D appearto be unified, forming the large EL display panel 10.

(Second Embodiment)

A second embodiment of the present invention will be described below.The components which are similar to those in the first embodiment aredenoted by the same reference numerals, and descriptions thereof areomitted.

In the second embodiment, the circuit section 22C of the TFT layer 22 isdisposed in a manner such that the TFT layer 22 is not bent at theboundary between the circuit section 22C and the pixel section 22P.

As shown in FIG. 9, the main transparent substrate 12 is provided with astep portion 30 formed by the adhesive layer 28 which is used forlaminating and fixing the EL display devices 14. The step portion 30 isprovided so as to change the positions of adjacent EL display devices 14in the thickness direction.

The height of the step portion 30 corresponds to the total thickness ofthe TFT layer 22 and the base layer 24. Accordingly, the circuit section22C may be disposed behind the adjacent EL display device 14 withoutbending the TFT layer 22.

(Third Embodiment)

A third embodiment of the present invention will be described below. Thecomponents which are similar to those in the first embodiment aredenoted by the same reference numerals, and descriptions thereof areomitted.

In the third embodiment, the circuit section 22C of the TFT layer 22 isalso disposed in a manner such that the TFT layer 22 is not bent at theboundary between the circuit section 22C and the pixel section 22P.

As shown in FIG. 10, in the third embodiment, the transparent electrodelayer (not shown) is laminated on the main transparent substrate 12 as afirst layer. In addition, the base layer 24 is provided as a secondlayer, and the TFT layer 22 is provided as a third layer. Accordingly,the transparent electrode layer, the base layer 24, and the TFT layer 22are laminated inversely compared to the manner in the first and thesecond embodiment. In addition, the thickness of the pixel section 22Pof the TFT layer 22 is double compared to that in the adjacent ELdisplay device 14, which is the standard thickness. The base layer 24 isfixed to the main transparent substrate 12 via an adhesive layer 28.

Accordingly, the circuit section 22C is disposed behind the adjacent ELdisplay device 14 without bending the TFT layer 22.

In the above-described second and third embodiments, the process ofbending the TFT layer 22 at the boundary between the circuit section 22Cand the pixel section 22P is not required. Thus, although modifications,such as changing of the thickness of the layers, are required, the TFTlayer 22 does not receive any load, so that problems, such as contactfailures, are avoided.

(Fourth Embodiment)

The following embodiment may only be applied when four EL displaydevices 14 are provided. FIG. 11 shows a first modification in which thefour EL display devices 14 are arranged in proximity to each other. Inthis case, four similar EL display devices 14 are prepared, and the twoEL display devices 14 disposed in the right side and the two EL displaydevices 14 disposed in left side are arranged inversely to each other.Accordingly, the circuit sections 22C of the TFT layers 22 are preventedfrom overlapping on the adjacent EL display devices 14.

(Fifth Embodiment)

FIG. 12 shows a second modification in which the EL display devices 14disposed at the right side and at the left side have differentstructures. More specifically, the circuit sections 22C are disposed atsymmetrical regions in the TFT layers 22. According to such a structure,the circuit sections 22C do not overlap on the adjacent EL displaydevices 14.

Although the large EL display panel 10 is constructed of the four ELdisplay devices 14A, 14B, 14C, and 14D in the present embodiment, it isalso possible to construct a larger panel.

FIG. 13 shows an actual manufacturing process of the EL panel 16 whichis used to achieve a large EL display panel 10.

The EL display devices 14 are formed by the processes shown in FIG. 13,which are described in order starting from the top. The order of theprocess is: forming TFTs→forming an insulating interlayer→formingcontact holes→forming a transparent electrode layer→formingbanks→forming a hole transfer layer→forming an EL layer→forming anelectrode layer.

INDUSTRIAL APPLICABILITY

As described above, the following advantages are achieved by the largeEL and the manufacturing method thereof according to the presentinvention. That is, in the case in which a plurality of EL displaydevices are arranged in a matrix pattern, the pitch between the pixelsprovided in the pixel section of the TFT array is maintained constant.

What is claimed is:
 1. A large EL panel, comprising: a main transparentsubstrate; a plurality of EL display devices which are arranged in amatrix pattern over the main transparent substrate, the plurality of ELdisplay devices being supported by the main transparent substrate, eachof said plurality of EL display devices including: a base layer overwhich a luminescent material is applied; an electrode layer which islaminated on one side of said base layer; and a TFT layer including: acircuit section in which light emission of the luminescent material iscontrolled by applying a predetermined voltage between said electrodelayer and said TFT layer; and a pixel section which is superimposed overanother side of said base layer opposite the one side and which isprovided with a plurality of pixels which divide said base layer intosections so that light emission of the luminescent material in eachsection is individually controlled by generating a potential differencebetween said electrode layer and said TFT layer at the correspondingsection, said circuit section of said TFT layer which is disposed at theregion outside a light emitting area being disposed behind an adjacentEL display device so that light emitting areas of the adjacent ELdisplay devices are arranged in proximity to each other to define apredetermined amount of gap, the TFT layers forming a TFT array havingan approximately constant pitch between the pixels in the pixelsections, and the predetermined amount of gap being equal to or lessthan the approximately constant pitch.
 2. The large EL panel accordingto claim 1, said plurality of EL display devices being at least twoinches in diagonal length, and said main transparent substrate being 20to 100 inches in diagonal.
 3. The large EL panel according to claim 1,said predetermined amount of gap between the light emitting areas of theadjacent EL display devices being approximately the same as a pitchbetween pixels provided in said pixel section of said TFT layer.
 4. Thelarge EL panel according to claim 1, said TFT layer being bent at aboundary between said pixel section and said circuit section so as todispose said circuit section of said TFT layer behind an adjacent ELdisplay device.
 5. The large EL panel according to claim 1, furtherincluding a step portion that changes positions of adjacent EL displaydevices in a thickness direction, the step portion being provided so asto dispose said circuit section of said TFT layer behind an adjacent ELdisplay device.
 6. The large EL panel according to claim 5, adjacent ELdisplay devices being inverted so as to arranged the base layers of theadjacent EL display devices in the same plane.
 7. An EL panel havingpixel sections, comprising: a first EL display element; a plurality offirst pixel sections arranged in the first EL display element, each ofthe first pixel sections being capable of emitting lights; a firstcircuit section controlling the emissions of the first pixel sections; asecond EL display element arranged adjacent to the first EL displayelement; a plurality of second pixel sections arranged in the second ELdisplay element, each of the second pixel sections being capable ofemitting lights; the first circuit section and the second EL displayelement overlapping with each other, a pitch between adjacent ones ofthe first pixel sections and the second pixel sections beingapproximately constant with a pitch between adjacent ones of the firstpixel sections, maintaining an overall equivalent distance separationbetween the pixel sections.
 8. An EL panel according to claim 7, furthercomprising: a second circuit section controlling the emissions of thesecond pixel sections; a third EL display element that overlaps with thesecond circuit section; and a plurality of third pixel sections arrangedin the third EL element, each of the third pixel sections being capableof emitting lights, a pitch between adjacent ones of the second pixelsections and the third pixel sections is approximately constant with atleast one of a pitch between adjacent ones of the first pixel sectionsand a pitch between adjacent ones of the second pixel sections.
 9. An ELpanel according to claim 7, wherein the second EL display element emitslight from a first side, and wherein the second EL element overlaps withthe first circuit section at a second side opposite to the first side.10. An EL panel according to claim 9, further comprising a substratewith transparency that supports the second EL display element from thesecond side thereof.
 11. An EL panel according to claim 10, furthercomprising an adhesive layer that adjoins the first EL display elementand the second EL element to the substrate.
 12. An EL panel according toclaim 7, wherein the first circuit section and the first pixel sectionsare connected with each other, and wherein the first circuit section isbent such that the first circuit section overlaps with the second ELdisplay element.
 13. An EL panel according to claim 7, furthercomprising a layer that fills a gap in thickness formed between thesecond EL display element and the first circuit section.
 14. An EL panelaccording to claim 7, wherein the thickness of the first circuit sectionis thinner than that of the first pixel sections.
 15. An EL panel havingpixel sections, comprising: a first EL display element; a plurality offirst pixel sections arranged in the first EL display element, each ofthe first pixel sections being capable of emitting lights; a firstcircuit section controlling the emissions of the first pixel sections; asecond EL display element having a plurality of second pixel sections,the second EL display element being arranged adjacent to the first ELdisplay element by overlapping the first EL display element; a secondcircuit section controlling the emissions of the second pixel sections,a pitch between adjacent ones of the first pixel sections and the secondpixel sections being approximately constant with a pitch betweenadjacent ones of the first pixel sections, maintaining an overallequivalent distance separation between the pixel sections.
 16. An ELpanel according to claim 15, wherein the first circuit section isarranged at a side that is not adjacent the second EL display element,and wherein the second circuit section is arranged at a side that is notadjacent the first EL display element.
 17. An EL panel comprising: afirst EL display element; a plurality of pixel sections arranged in thefirst EL display element, each of the first pixel sections being capableof emitting lights; a circuit section of the first EL display elementcontrolling the emission of the pixel sections; a second EL displayelement overlapping the circuit section and having other pixel sections;a substrate that supports the first and the second EL display elements;and a layer for filling a gap in thickness formed between the second ELdisplay element and the circuit section that are overlapped, an overallequivalent distance separation being maintained between the pixelsections.
 18. An EL panel according to claim 17, the layer including anadhesive that adjoins at least one of the first EL display element andthe second EL display element to the substrate.